While retouching an image for Melbourne based Photographer Jayden Harrod, I noticed a significant slow down of my machine when my file size started to creep upwards of 500mb. It was extremely frustrating as I use a relatively new iMac and one would assume that this machine could handle the work I was doing.

Photoshop is just like any other program out there, it will do things and function in what ever way you tell it to. So, if you’re telling it to do things like not allowing it to use enough RAM or not giving it any space to store temporary files then you’ll notice a significant slow down in performance when you’re working on high resolution files.

So, lets have a look at what you can tell Photoshop to do in order for it handle your massive files a little better.

If you’re on a mac. You need to go to Photoshop -> Preferences -> Performance.

For Windows head over to Edit -> Preferences -> Performance.

Memory Usage.

This is where you tell Photoshop how much of your RAM it can use. When I retouch, I only really have iTunes and Photoshop open so I generally leave this at around 80-90% If you don’t give Photoshop enough RAM it will begin to store files on a Hard Drive which is slower to access then RAM. Consider closing unused applications when you’re using Photoshop.

Scratch Disks

Scratch Disks are Hard Drives that you tell Photoshop to use when it needs more space then you have available in RAM. If you have the cash and the hardware consider installing a Solid State Drive in your machine. I would, but I can’t add another drive inside my iMac. So, I just leave it assigned to my primary internal drive. I just have to make sure I don’t fill up this drive.

For those that want to consider adding another drive to your iMac using eSATA for maximum speed you can. It involves some drilling which is something I’m too scared to try. Find the information here.

History & Cache

I work very non-destructively, meaning, if I make a mistake I can always step backward with out undoing a million times. I’ve developed a workflow that enables me to work through a whole image and undo everything if I need to. Which means, I only need to set my History States to 20. Think about it, the more History States you tell Photoshop to remember, the more space it will need to store them. Keeping this number as small as you can will improve performance. If you notice a big slow down while working consider purging. To do this go to Edit -> Purge -> All.

Cache Levels is a little bit of a mystery to me. Photoshop tells me it is used to improve screen redraw speed. I normally set it to about 6 because the majority of files I work with are quite large.

Cache Tile Size. This little guy was the reason for my pain. I had never touched this setting previously purely because I had no idea what it was. It turns out that the default setting of 128k severely impaires performance. After changing from the default value of 128k to 1024k I really noticed a substantial increase in speed with brush strokes and filters.

GPU Settings

Keep this ticked if you have a Graphics Card that supports it. It enables you to pan flick around your documents and other fancy little thingys. Turn it off and a few things will be disabled which you probably won’t notice unless you use the 3D tools a lot.

Efficiency Indicator.

Keep an eye on this little guy at the bottom of your document window. To access it, click on the little arrow and make sure Efficiency is ticked. When it starts to drop below 100% Photoshop is telling you it is struggling to keep up!

Finally I need to thank the clever people/person responsible for macperformanceguide.com After running in to trouble I came across this site and they enlightened me about the little Cache Tile Size ‘trick’. This alone purely solved my problem.

Click to view the helpful guide

I hope this helps you maximise Photoshop’s performance while retouching.